Field
Aspects of the present invention generally relate to a power transmission device, a power transmission method, and a storage medium.
Description of the Related Art
Conventionally, techniques for feeding power in a non-contact manner (wirelessly) have been known. The following four methods are used for feeding power in a non-contact manner: an electromagnetic induction method, a magnetic resonance method, an electric field coupling method, and a radio wave reception method. Among these four methods, the magnetic resonance method is characterized in that sufficient power can be transmitted and a long power transmission distance can be ensured. Thus, the magnetic resonance method is particularly drawing attention among the four methods. For example, as such magnetic resonance method, by utilizing this power transmission distance, Japanese Patent Application Laid-Open No. 2009-136132 discusses a 1-to-N power feeding method for allowing a power transmission device to transmit power to a plurality of reception devices wirelessly.
According to the technique discussed in Japanese Patent Application Laid-Open No. 2009-136132, in a standby mode in which the power transmission device is not transmitting power, the power transmission device transmits certain pulse signals to determine whether any power reception device has come close within a few meters of the power transmission device. If a reception device transmits its own unique identification data (ID) to the power transmission device, the power transmission device determines whether the source that has transmitted the unique ID is a power reception device as a power feeding target. If the wireless power reception device is determined to be a target, the power transmission device feeds power to the power reception device. The power transmission device can feed power to a plurality of power reception devices while switching the power feeding targets in a time-division manner.
Regarding wireless power transmission techniques, improvement in transmission efficiency is demanded. Efficiency of power transmission from a power transmission device to a power reception device depends on the length of power transmission time by the power transmission device. More specifically, longer power transmission time results in higher transmission efficiency. However, in a time-division power feeding method, if the power transmission time for one power reception device is extended, the power transmission start time for the next power reception device is delayed, which is a problem.